The present invention relates to a process for attaching a blade to a turbine blade support, such as a rotor or rotor disc, of a turbine.
A turbine blade is typically attached to a turbine through a blade root which is disposed within a complementary groove in the rotor or a rotor disc of the turbine rotor. Modern steam turbines and gas tubines often employ a blade attachment design in which the blade roots and rotor or rotor disc grooves are substantially triangularly shaped and include multiple serrations. This design is intended to provide sufficient contact between the blade roots and the steeples, the portions of the rotor or rotor disc between the grooves, so that the maximum operating stresses do not exceed the fatigue strength of the materials from which the blade and blade support are formed. The blade root and groove machining tolerances are critical as even a fraction of a mil mismatch can result in excessive operating stresses at the blade root or the steeple. Because of this concern, very sophisticated machining and inspection techniques are required to manufacture and qualify blades for service applications. Often, many blades must be rejected before one with a properly shaped root is found for a particular groove. This problem becomes even more complex in the reblading of a rotor or rotor disc during a service overhaul since wear on the serrations of the steeple can result in the new blades not fitting properly within the groove.
Thus, it is desired to develop a method for attaching such blades to a blade support that overcomes the aforementioned difficulties.